This is the polite term tennis uses when a player quits in the middle of a match. If you see a tennis result that reads, for example, Petkovic d. Stosur, 6-3, 1-0, ret., it means that Stosur retired, or quit, during the match when Petkovic was leading 1-0 in the second set. The most common reasons players retire are injury and illness. Fans of Andy Roddick recall that he retired in the second round of the Australian Open this year.